1.Field of the Invention
This invention is in the field of token-passing local-area networks and more particularly relates to an improved method by which one module of such a network initializes the network by transmitting a token to sequentially addressed module addresses of the network until a token is accepted by an addressed module.
2.Description of the Prior Art
In any token-passing local-area network where a single communication medium is shared by many modules, there must be a method by which the modules of the network when energized determine if the network is initialized and, if not, which module is to initiate forming the properly functioning modules of the network into a logical ring. In token-passing local-area networks a module which has accepted a token from another module has exclusive access to the medium to transmit information to other modules normally for a limited period of time, at the end of which period the module having the token must transfer the token to another successor module.
To do this, a special frame, a series or set of binary digits called a token pass frame, or a token, is transmitted from one module to another module around a logical ring formed of the modules of the network. The physical address of each module establishes its position and order in the ring. While a module has access to the medium, or has the token, it is permitted to transmit information, an information frame, to one or more modules of the ring before passing a token to a successor module.
To initialize a token-passing local-area network in which each of the modules is the peer or equal of all the others; i.e., there is no master, or control, module as such, particularly where several modules of a given network can be energized substantially simultaneously, there is a need to determine which of the modules so simultaneously energized is to be the initiator, or the initiating module. This is typically accomplished by some form of a contention process. When the initiating module is identified in prior art networks, the initiating module typically transmits a signal, or set of signals, which the first module to accept has the token, or the authority to transmit over the network medium.
A problem with prior art methods of initialization of token-passing local-area networks is that they lacked a systematic way of addressing each possible network position, or possible address of a module, and particularly a method which was consistent with the method of passing tokens between modules of an initialized logical ring formed by the properly functioning modules of the network.